The different events are:
An md array which previously was configured appears to no longer be configured. (syslog priority: Critical)
If mdadm was told to monitor an array which is RAID0 or Linear, then it will report DeviceDisappeared with the extra information Wrong-Level. This is because RAID0 and Linear do not support the device-failed, hot-spare and resync operations which are monitored.
An md array started reconstruction. (syslog priority: Warning)
Where NN is a two-digit number (ie. 05, 48 ). This indicates that rebuild has passed that many percent of the total. The events are generated with fixed increment since 0. Increment size may be specified with a commandline option (default is 20). (syslog priority: Warning)
An md array that was rebuilding, isn't any more, either because it finished normally or was aborted. (syslog priority: Warning)
An active component device of an array has been marked as faulty. (syslog priority: Critical)
A spare component device which was being rebuilt to replace a faulty device has failed. (syslog priority: Critical)
A spare component device which was being rebuilt to replace a faulty device has been successfully rebuilt and has been made active. (syslog priority: Info)
A new md array has been detected in the /proc/mdstat file. (syslog priority: Info)
A newly noticed array appears to be degraded. This message is not generated when mdadm notices a drive failure which causes degradation, but only when mdadm notices that an array is degraded when it first sees the array. (syslog priority: Critical)
A spare drive has been moved from one array in a spare-group or domain to another to allow a failed drive to be replaced. (syslog priority: Info)
If mdadm has been told, via the config file, that an array should have a certain number of spare devices, and mdadm detects that it has fewer than this number when it first sees the array, it will report a SparesMissing message. (syslog priority: Warning)
An array was found at startup, and the --test flag was given. (syslog priority: Info)
Only Fail, FailSpare, DegradedArray, SparesMissing and TestMessage cause Email to be sent. All events cause the program to be run. The program is run with two or three arguments: the event name, the array device and possibly a second device.